The difficulty in implementing efficient socket contacts (electrical plug connectors) is, in response to overall space for the plug connections that is getting smaller all the time, to allow to be effective sufficiently great contact normal forces at the contact places between the contact lamellae of the socket contacts and the contact pins (contact blades) of the mating connectors. These contact normal forces are to be designated as being sufficient if they ensure an electrically conductive contact, even in the case of extraneous layers on the metallic surfaces of the contact partners, that is, when such extraneous layers are not pushed through with certainty.
FIG. 2a shows a known electrical plug connector (socket contact) 20a into which a contact pin is plugged. In this plug contact 20a, a current-conducting contact element 21 having a resilient contact lamella 22 is made of a contact material which has a sufficiently great relaxation stability, even at high working temperatures, to counter an inadmissible decrease in the contact normal force over long periods of use. These relaxation-stable and sufficiently conductive contact materials are, however, comparatively expensive.
Apart from that, other electrical plug connectors (socket contact) are known in which, in addition, force support springs (leaf springs), made of materials that are the same or materials that are not the same, assist, by mechanical coupling with the contact lamellae, in achieving the desired contact normal forces at the contact points and in ensuring them in a durable manner. FIG. 2b shows a known plug connector 20b having a force-supporting spring 23 of the same material, which is made by a material doubling of contact element 21 and acts upon contact lamella 22. FIG. 2c shows a known plug connector 20c having a leaf spring that is not of the same material (cantilever steel spring) 24, which is formed by a tab set in facing inwards of a steel sleeve 25 that surrounds current-conducting contact element 21, in order to support contact lamella 22 of contact element 21 with respect to the contact normal force. The advantage of such cantilever construction systems is that steel spring materials have a clearly higher relaxation stability, in the working temperature range striven for, than the copper-based alloys used for contact element 21. It is true, though, that one disadvantage of these cantilever construction systems is that the steel sleeve, as a rule, completely surrounds approximately one-half of the contact element, which means a substantial material usage, and with that, high costs.